Honeycomb structures are in use as a carrier for a catalyst having a catalytic action, for use in internal combustion engine, boiler, chemical reactor, fuel cell reformer, etc. and a filter for trapping particulate matter present in an exhaust gas, particularly particulate matter emitted from a diesel engine.
In the honeycomb structure used for such a purpose, the sharp temperature change of exhaust gas and the local heating makes non-uniform the temperature distribution inside the honeycomb structure and there have been problems such as crack generation in honeycomb structure and the like. When the honeycomb structure is used particularly as a filter for trapping a particulate matter in an exhaust gas emitted from a diesel engine (hereinafter the filter is referred as DPF), it is necessary to burn the fine carbon particles deposited on the filter to remove the particles and regenerate the filter and, in that case, high temperatures are inevitably generated locally in the filter; as a result, cracks have tended to be generated by a large thermal stress.
Hence, there have been proposed processes for producing a honeycomb structure by bonding a plurality of individual segments using a bonding agent. In, for example, U.S. Pat. No. 4,335,783 is disclosed a process for producing a honeycomb structure, which comprises bonding a large number of honeycomb parts using a discontinuous bonding agent. Also in JP-B-61-51240 is proposed a thermal shock resistant rotary regenerative ceramic heat exchanger which is formed by extrusion forming a matrix segment of honeycomb structure made of a ceramic material; firing them; making smooth, by processing, the outer peripheral portion of the fired segment; coating the part subject to bonding of the resulting segment with a ceramic bonding agent which turns, after firing, to have substantially the same chemical composition as the matrix segment and a difference in thermal expansion coefficient of 0.1% or less at 800° C.; and firing the coated segments.
Also in the SAE paper 860008 of 1986 is disclosed a ceramic honeycomb structure obtained by bonding cordierite honeycomb segments with a cordierite cement. Further in JP-A-8-28246 is disclosed a ceramic honeycomb structure obtained by bonding honeycomb ceramic members with an elastic sealant made of at least a three-dimensionally intertwined inorganic fiber, an inorganic binder, an organic binder and inorganic particles.
The honeycomb structure arranged as described above is ordinarily manufactured by forming honeycomb segments having cells disposed parallel to a central axis of the honeycomb segment, each cell being surrounded by porous partition walls functioning as filters, and each cell functioning as a fluid passage, combining the honeycomb segments to form a crude honeycomb structure, and processing a peripheral portion of the crude honeycomb structure in a predetermined shape. Since the honeycomb structure manufactured as described above is accommodated in a metal can body and the like for use, it must be processed so that it has an outer peripheral shape corresponding to an inner shape of the metal can body and the like. That is, it is necessary to manufacture a honeycomb structure from the crude honeycomb structure described above by processing the peripheral portion of the crude honeycomb structure in a shape corresponding to the inner shape of the metal can body and the like in which the crude honeycomb structure is accommodated.
There has been known a method of processing the peripheral portion of the crude honeycomb structure by a grinder, for example, a cam grinder, a cylindrical grinder, and the like as a method of manufacturing the honeycomb structure. For example, there have been proposed a method of manufacturing a honeycomb structure by grinding a porous ceramic material to various sizes and shapes using a grind member having grind stones disposed on the circumferential portion of a disc, and a method of manufacturing a honeycomb structure having various shapes by moving a position of a grind member in synchronism with rotation of a porous ceramic material under numerical control (NC) using a computer (JP-A-2001-191240).
In the methods described above, however, when a body to be ground(a body to be processed) is a crude honeycomb structure 102 formed by combining a plurality of honeycomb segments 101 as shown in FIG. 5 and peripheral portions of the crude honeycomb segments 102 are processed by the grinder, for example, the cam grinder, the cylindrical grinder, and the like, there is a problem in that a processing speed is restricted in a range in which the crude honeycomb structure 102 is not broken. This is because a rotating direction of a grind stone 103 is in coincidence with a direction in which the honeycomb segments 101 are exfoliated and the crude honeycomb structure 102 is broken on a bonding surface 104 of the honeycomb segments 101 constituting the crude honeycomb structure 102. Accordingly, the above methods are disadvantageous in that the crude honeycomb structure 102 cannot be effectively processed.
Moreover, when the crude honeycomb structure 102 is formed in a shape having corners, for example, it is a rectangular parallelepiped as shown in FIG. 5, there is also a problem in that a probability of breakage of the crude honeycomb structure 102 is increased by an impact generated when a corner portion of the crude honeycomb structure 102 is ground by the grind stone 103. Further, since the body to be ground is the porous ceramic material and has a high processing resistance due to its hardness, the grind stone 103 is worn at a high speed (has a short life as a tool), from which a problem arises in that these methods are not advantageous in cost.
The present invention has been made in view of the above situation and aims at providing a method which can be low in cost and efficiently manufacture a honeycomb structure suitably used as a carrier for a catalyst having a catalytic action, for use in internal combustion engine, boiler, chemical reactor, reformer for fuel cell, etc., or as a filter for trapping particulate matter present in an exhaust gas.